Methods to generate fracture toughness values of materials, such as metallic and ceramic materials, have been recommended by the American Society for Testing and Materials (ASTM) and widely accepted as standard test methods by the scientific community. A wealth of test data has been obtained by these methods and reported and evaluated for many types of materials. However, the data shows scatter and inconsistency even within a family of the same material type and the differences appear irreconcilable. Lack of provisions to account for specimen size effects, in homogeneity of materials and other factors can be cited as causes of these inconsistencies.
Inconsistencies in fracture toughness evaluation can be further complicated when evaluating welds which inherently consist of three zones of different phases known as the weld zone, the heat affected zone, and the base material. Each of these zones is likely to manifest a characteristically different microstructure and mechanical properties. The fracture behavior of the fused line that lies between the solidified weld zone and the heat affected zone is not well explored due to the lack of standard test methods for these types of structures.
In addition, influences of gasses or other environmental features on the behavior of a weldment are not well known, but the information is important and needed for energy development programs. In particular, the influence of hydrogen on materials and particularly weld zones is important information that is missing or inconsistent in the current literature. The conventional methods of measuring in-situ crack behavior of weld material are typically not physically suitable or economically viable in extremely high pressure environments of hydrogen.